[QLab] Live Multicamera

[Tim Thomson]

Has anyone any experience they can lend as far as bringing in multiple
live cameras on stage simultaneously into QLab for discrete projector
routing? I have an instance in a show wherein two actors will each
use a live camera simultaneously, and we'd like to route each signal
to its own screen. I don't seem to be successful in bringing in a
composite signal of any stripe over a stage-to-booth distance that
QLab recognizes as a camera source - much less two at once. Anyone
have any thoughts? Is there a simple SD analog to digital converter
that can be used in multiple configuration?

Thanks -

-=Tim
________________________________________________________
WHEN REPLYING, PLEASE QUOTE ONLY WHAT YOU NEED. Thanks!
Change your preferences or unsubscribe here:
http://lists.figure53.com/listinfo.cgi/qlab-figure53.com
Follow Figure 53 on Twitter here: http://twitter.com/Figure53

[luckydave]

The Canopus ADVC units seem to be pretty successful for A/D conversion, although the DV encoding does take a little bit of time, so there's typically a lag of a few frames. Putting that unit next to the computer (multiple units for multiple cameras, of course), and sending the composite signal through a distribution amplifier should take care of your needs, as long as a little bit of lag is allowable.

Here's a link:

http://www.grassvalley.com/products/advc-hd50

luckydave
luck...@figure53.com

[Tim Thomson]

Excellent, thank you. I guess I just wanted that little extra bit of
confidence that we have seen Qlab see multiple a/d converters as
multiple cameras. If so, perfect.

-=Tim

[Christopher Ashworth]

Hi Tim,

Here's a showcase from Sam that may provide additional useful info:

http://figure53.com/qlab/showcases/frost-nixon/

(Thanks, Sam.)

[Jason Eckenroth]

I was thinking of that showcase when I saw this post. However: Frost/nixon used multiple cameras through a switcher and a single canopus adv, while here he's asking about multiple camera inputs to QLab directly, potentially via multiple advs. Does QLab allow for this?

[Tim Thomson]

Exactly Jason, and thank you, that cuts to the core of it. I have a
switcher, and I wish it were that simple :) But yes, where two
screens are throughout most of the show a canvas for QLab-played
prerecord material, at one point two cameras have to route
simultaneously to one screen each.

We're only running SD, though, and have composite wired under the
stage; I have two ADVC55's coming tomorrow which I trust will do the
trick. The main problem I had was that an earlier test used a smaller
Grass Valley mini a/d converter which went in USB, and QLab didn't
ever recognize it as a source. (In fact, an audio codec associated
with it crashed QLab entirely.) So I appreciate the extra bit of
confidence that this isn't necessarily so with the FireWire
converters.

Thanks all.

[Christopher Ashworth]

On Jan 20, 2011, at 6:07 PM, Jason Eckenroth wrote:

> Does QLab allow for this?

Good question, and yes. As you add devices to the FireWire bus, bandwidth becomes a concern, but I've definitely tested with multiple FireWire cameras running at the same time before.

-C

[Ben Chaisson]

Hi

I would suggest that qlab might not be the best choice for mulitple camera work because you will get a few frames of lag or delay.
Perhaps a mulitformat switcher that can take signal from Qlab before going to your projector(s) might be a better option.
but if you must the canopus Avdc will bring Composite or S video into qlab.
you will need one per camera.
if you are doing this on a mac pro you might try a black magic intensity card  as it is PCI and will have some less lag.
Ben

---

From: Tim Thomson <t...@hotpixelaction.com>
To: ql...@lists.figure53.com
Sent: Thu, January 20, 2011 5:10:24 PM
Subject: [QLab] Live Multicamera

[sam kusnetz]

> I would suggest that qlab might not be the best choice for mulitple camera work
> because you will get a few frames of lag or delay.

to be clear, it's the DV codec itself that results in the lag time, and it's a specific amount: two frames delay on encode, and two frames delay on decode. so any device which encodes incoming video using the DV codec will result in a guaranteed minimum of four frames of delay.

> Perhaps a mulitformat switcher that can take signal from Qlab before going to
> your projector(s) might be a better option.

i'm not sure what this would be for... the only delay you're going to see in this scenario is on the input side. video out from qlab to the projectors should be relatively trouble-free.

> if you are doing this on a mac pro you might try a black magic intensity card
> as it is PCI and will have some less lag.

while it will likely have less lag, it will not work with qlab. we bought a black magic for frost/nixon but it does not appear as an available input. i'm afraid i do not remember the details of why, all i remember is that i spent three days trying to get it to work using all manner of tools. i also tried to get a DFG1394 to work. no dice.

the canopus is the way to go, assuming the four frames of lag time is acceptable to you.

cheerio
sam